Wiki info about La-5FN

The Lavochkin La-5 was a single-engine monoplane fighter, a single-seater with an enclosed cockpit, wooden frame and a canvas skin. FN in the designation stands for Boosted, Fuel Injection. The new variant entered production and began to reach front-line units in March 1943. The La-5FN, rather than being a successor to the earlier La-5F, was produced concurrently. Its ASh-82FN engine could reach 1,850 HP and remain at takeoff power settings for up to 10 minutes.
In April 1943 a serial La-5FN was flight tested in mock combat against a captured Bf-109G-2. The Soviet aircraft proved superior at low and medium altitudes, the most common on the Eastern Front. The La-5FN was superior both in top speed as well as maneuvering in the vertical. An analysis of these engagements led to significant changes in Soviet tactics. The La-5FN's armament was identical to that of the La-5 and consisted of twin 20mm ShVAK cannon with 200 rounds per gun. The guns were pneumatically or mechanically operated.